In recent years, light-emitting diode elements (referred to as LED elements) have widely been used for a backlight of a color display, illumination or the like, because the LED elements are semi-conductor light-emitting elements and have a long service life and excellent driving characteristic, and further have a high light-emitting efficiency and bright light-emitting color.
In particular, recently, there are widely adopted light-emitting devices including LED elements that are electrically connected in series and driven by the voltage rectified from the AC voltage. The number of LED elements connected in series are switched, depending on a voltage level or current level of the voltage that is rectified from the AC voltage of an AC power source.
As a method for utilization of an illumination device, if a plurality of LED elements are connected in series, because a combination of LED elements has flexibility and a degree of freedom in shape, it is proposed to use the combination for an advertisement or decoration by deforming the combination (for reference, see PTL 1).
A conventional light-emitting device as disclosed in PTL 1 is described hereinafter with reference to FIG. 10.
The conventional light-emitting device includes a plurality of light-emitting blocks C1 to C7. Each of the light-emitting blocks includes two to four LED elements which are connected in series. The light-emitting blocks C1 to C7 are arranged in any shape to display a character and so on.
An object of the conventional light-emitting device is to display information, such as a character, a sign in an advertisement and a decoration, by properly arranging a plurality of light-emitting blocks. The conventional light-emitting device discloses a structure with a changeable length of connecting light-emitting blocks that are connectable to a standard light-emitting block. However, it does not disclose a light-emitting area including a first light-emitting element and a second light-emitting element to be lit separately or together in accordance with a voltage value change due to an alternate current, a drive condition, light-emitting intensity and so on of the light-emitting blocks are not at all disclosed.